Release date: September 29, 2020
Aluminum trichloride is mainly used as a catalyst, which is needed in the production of alkylbenzene, ethylbenzene, cumylphenol acetone, ethyl chloride, dye intermediates and petroleum resin. In the famous Friedel-Crafts reaction, ethylbenzene, acetophenone, some drugs and vat dyes were prepared with aluminum trichloride as catalyst.
Aluminum trichloride is also widely used in non-catalysts. It is not only used as a nucleating agent for titanium dioxide pigments, but also used to manufacture aluminum hydride boron, lithium aluminum hydride, the preparation of various aluminum compounds and the refining of petroleum products.
There are three manufacturing processes of aluminum trichloride: aluminum ingot method, alumina powder method and salt bath method. Among them, although there are patent reports on salt bath method, there are no reports on industrial production.
Aluminum ingot method: it is made by direct reaction of aluminum ingot and chlorine gas. The specific reaction process is as follows: in a chlorination reactor built of refractory bricks, chlorine gas continuously flows into the aluminum liquid layer in the reaction chamber of the chlorination reactor from the upstream pipeline to form a bubbling state, and contacts with the aluminum liquid to carry out the following reaction:
2a 1+3c 12-. 2 AIC 13
Because the reaction is carried out in a strong exothermic state, the heat of the reaction is enough to make the aluminum ingot continuously melt in the aluminum liquid layer in the feed chamber, and the molten aluminum liquid continuously passes through the sealing partition between the feed chamber and the reaction chamber, and then flows into the reaction chamber from the feed chamber, so that the aluminum liquid keeps a certain level and reacts with chlorine gas. Because the reaction heat is enough to melt the aluminum ingot, it is necessary to remove the excess reaction heat by natural heat dissipation of molten aluminum or adding a cooling jacket outside the reaction chamber. More importantly, the feeding speed of chlorine gas should be controlled to prevent excessive reaction and excessive reaction temperature. Generally, the reaction temperature should be kept slightly higher than the melting temperature of aluminum, preferably between 700 and 800 degrees.
The aluminum trichloride gas generated by the reaction is introduced into the trap through a sublimation tube, and the aluminum trichloride gas at the entrance of the trap is generally controlled between 190 ~ 200 degrees, so that the aluminum trichloride gas can crystallize and precipitate on the trap wall after entering the trap (the sublimation temperature of aluminum trichloride is 180.6 degrees under normal pressure), and the product is discharged from the bottom of the trap. The tail gas is discharged after washing with water and alkali.
The aluminum ingot process has a short process flow, and the main equipment is only chlorination reactor and catcher, so the requirements for materials are not high. Refractory bricks are generally used in chlorination reactors, and carbon steel can be used in traps, so the investment per unit product is very small, the products can reach the quality level, and aluminum chips can be used as raw materials. These are all advantages. However, because there is little waste aluminum, most factories basically use aluminum ingots as raw materials. Compared with alumina powder method, the cost of raw materials is 8. Especially at present, aluminum is a tight material, and the shortcomings of aluminum ingot method are more prominent when the price of aluminum rises.
Alumina powder method: the raw materials of this method are alumina powder and chlorine gas, which react in the presence of reducing agent carbon to produce aluminum trichloride. Carbon is an ancient reducing agent, which has three different forms: solid, liquid and gas. The solid is coal and coke, the liquid is heavy oil, and the gas is carbon monoxide. In China, petroleum coke is used as reducing agent.
The time to prepare aluminum trichloride from alumina powder is much earlier than that from aluminum ingot. Data show that 1824 aluminum trichloride is prepared from alumina powder abroad. At that time, the price of aluminum was very expensive, and aluminum trichloride was used to prepare metallic aluminum. Later, due to the success of producing electrolytic aluminum by Hall method and the progress of producing high-purity alumina by Bayer method (Hall method needs high-purity alumina to produce electrolytic aluminum), aluminum trichloride produced by alumina powder method was gradually replaced by aluminum ingot method.